زَيْدٌ أَبُوهُ قَائِمٌ
Zayd's father is standing.
Zayd is the outer topic, but the attribute of standing is directly assigned to his father. The report concerns Zayd by way of a related person; it does not say that Zayd himself stands.
«Abūhu» is the inner subject and «qāʾim» its predicate. The whole inner nominal clause is the outer predicate, with «-hu» providing the link. Distinguishing those two levels of predication is the core of sababī analysis.